Importance of Lithography Technology for Patterning on Curved Surfaces
Large-area electronic, mechanical and electromechanical structures on curved surfaces with integrated functional capability are rapidly growing in significance in a number of applications. In the military environment, this is evidenced by the desire for faster, lighter, and greater-functionality hardware, requiring active electronic circuitry and/or large-area micromechanical structures such as sensors and actuators. In the commercial sector, the availability of active microelectronic devices and micromechanical structures on large surfaces, especially those printed conformably on curved surfaces, holds enormous promise for applications in communications, integrated sensors and controls, and medical sectors. Technologies currently do not exist to produce such devices and structures.
As the level of functionality in a microelectronic or micromechanical device or structure increases, it becomes more important to develop manufacturing technologies and systems that will enable large-area printing on curved substrates at a reasonable cost. The curvature of the substrate may be predetermined and well defined, e.g., a spherical shell of known radius, or it may be random and unknown, e.g., a random, two-dimensional topography variation combining concave and convex regions. Existing approaches are unattractive because they provide very low throughputs (e.g., electron-beam or other focused-beam direct writing), or involve expensive additional process steps (e.g., chemical-mechanical polishing), or have a short depth of focus, and they cannot print conformably (e.g., all existing optical projection lithography techniques). This invention discloses a new lithography technology that enables conformable patterning with high resolution and high throughput on large-area substrates which may have curvature in one or more directions.
In the manufacturing of electronic devices and modules, the production equipment represents a major cost element, accounting for approximately two-thirds of the total facility cost. Of the many process steps involved in the fabrication of such devices, the most critical are those required for successively patterning various layers of photoresist and other materials. The capabilities and cost-effectiveness of the lithography technology impact the performance and cost of the device, and ultimately determine the size and cost at the end-system level. This makes patterning tools the largest and most critical component of the total production equipment investment. Typical costs of individual tools range between $2 and 5 million. A high-volume production facility would have multiple lithography tools. In addition, operating expenses add several hundred thousand dollars per year to the net cost of running such tools. Thus, in order to make significant progress toward broad realization of greater-functionality electronic and mechanical systems, there is a need to develop and implement new high-resolution, high-throughput lithography equipment for conformable patterning on curved, large-area surfaces.